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Post by stewartm on Sept 24, 2016 7:51:56 GMT 11
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Post by jake on Sept 24, 2016 14:03:33 GMT 11
It would be interesting to see a 30 kw used pack and to see someone put that in an older model. Nissan engineers have confirmed it is possible.
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Post by 4wardthinking on Sept 25, 2016 16:30:02 GMT 11
If it can go in physically, the rest is 'tronics fiddlery!!.
Best plan would be loom and ECU's from s wrecked one, but these packs are well sought after.
The big question is if it is worth doing?.
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Post by jake on Sept 26, 2016 2:32:55 GMT 11
There is no problem fitting it in. It is the same dimensions as the old pack but it would require the adaptor kit which is readily available. I'm also not sure if there is anything stopping the pack being fitted electronically. As I said Nissan engineers have confirmed its possible.
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Post by 4wardthinking on Sept 26, 2016 12:13:07 GMT 11
The whole charge and monitoring needs to encompass the capacities & monitoring to be able to control it efficiently.
It's not possible to just put higher spec modules in, and simply take advantage of the properties of them.
The system(car) knows how much energy is pushed in & out as it operates, and anything beyond its algorithms will throw alarms out at the driver.
Imagine one day it has a useable 10kw, and next day it has 12kw. It's expecting current demand/production to leave modules at a certain voltage, but suddenly the voltage it read previously at say 60%, is not giving that voltage anymore, it indicates 54%. The system will go into panic mode. The power it fed in has not equated to what it used to, and is possibly leaking away, or the pack is not storing it as it used to do.
The chemistry in the pack relies largely on voltage to indicate state of charge. So say a cell at twice the capacity received the same charge as one at 50%, the voltage will differ. Problem is the car knows how much it fed into the pack, and has its expectations, which will cause it to alarm, as it may consider the energy I could be disappearing as heat. That's how the car doesn't blow the pack up. Safety is paramount given adverse publicity for Lithium based electrochemistry.
It can be done, but you'll need the wiring loom & ECU's too.
Ripping the car apart to actually use a higher capacity pack may be tedious unless you have a scrap one, space & time.
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Post by jake on Sept 27, 2016 2:08:00 GMT 11
I''m just guessing here but Nissan might have designed the electrics to cope with the higher capacity pack and possibly larger. Here's hoping.
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Post by lesmando24 on Sept 27, 2016 9:37:34 GMT 11
I think Nissan said the opposite, the electronics in a 24kWh model can't recognise 30kWh, so there is no upgrade path. They didn't say why. Someone theorised it was the GID count from the battery controller confusing the main computer.
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Post by jake on Sept 28, 2016 2:04:25 GMT 11
I thought I read somewhere that the charger was the same for the 24kw and 30 kw but I don't know what else. There could be other components that are incompatible that I don't know about and I know the software would need an update. Oh well, a man can dream.
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Post by kris on Sept 30, 2016 18:13:30 GMT 11
Interesting conversation. I've seen piggy-back battery packs that mount in the rear parcel area & parallel the main traction pack. They also charge via the onboard AC charger but have their own BMS. The fact that these tack ons work suggests that the car's management system can cope with extra capacity/range? I'm puzzled as to why having higher capacity cells in the main pack (rather than as a piggy back) should cause the predicted havoc with the main computer?
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Post by 4wardthinking on Sept 30, 2016 18:40:22 GMT 11
The car cannot keep track of two BMS services.
It either uses one or the other.
Parallel packs would cause a Big Bang, unless they are perfectly matched too.
The vehicle knows how much power has been fed in, and how much has been drawn out.
The complications come when it tries to predict range on a large capacity pack, but gets less than it expects as the pack begins to fade.
The car measures it's state of charge etc via the above, and terminal voltage being Lithium based.
Now put a greater capacity in there, feed in 24kw(ex for simplicity), it would expect the terminal voltage to be around 4.11v, yet in a higher capacity pack, the terminal voltage will be less.
So, it counts the power in, and expects a certain voltage to be confirmed at terminal ends. A higher capacity pack will show as power in referenced to terminal voltage as down.
Charging the pack to remain useable for many years relies on a complex set of algorithms being processed at all times the car is active.
Now it works out what modules are failing by actual and theoretical readings too. It knows every cells voltage as it should be given power it has been fed, and attempts to balance the pack constantly too.
These things are all based on what it has been instructed about the pack, change the capacity, and you must change all the parameters so it can manage it efficiently, give it any curved balls, and it will come up with exceptions, and throw out errors, more than likely it will go into preservation mode, and shut down.
Brief I know, but it quickly covers a very complex process. Hope this helps.
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Post by 4wardthinking on Sept 30, 2016 18:54:10 GMT 11
Then add the further problem of power delivery.
The system requests power from the pack, it tells it how much is available, and on regen, it tells it how much it can take, the car tailors its performance to what the can-bus flicks around for it.
The BMS is indeed independant, but is subject to a watch-dog service, and a few other 'safety' extras forced upon it, including impact emergency disconnect.
A piggy back I'd like to see work. I've seen all the pictures. And the engineer ones too, but they don't stand the test of time sadly.
The power cannot be simply switched over. The car has no way of determining the packs parameters, it only works on what it is pre-programmed. A good prod around with service diagnostics shows the packs parameters.
Tuning the cars would be easy if it was just about pack size. It's how the car uses any power is the complex part, and making it reliable for the average owner, day in, day out, and then re-gaining other-wise wasted energy.
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Post by EVangelist on Sept 30, 2016 19:30:42 GMT 11
I'm not an expert in this, but I would have thought it would be possible to put a bigger battery into an EV (assuming mechanical & electrical fit) and have it all work, provided the car's software to manage it all was correctly updated to recognise it, charge it correctly, discharge it correctly, have the dash displays read correctly etc.
I don't see why there would need to be any changes to the existing hardware elements - it should all be software.
So it's a question of manufacturer will to do it, not capability to do it. So when a manufacturer says they "can't" do it, I read that as they "don't want" to do it.
All IMHO.
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Post by 4wardthinking on Sept 30, 2016 21:46:19 GMT 11
Indeed.
Doesn't sell cars otherwise. They are in business to make profit, we all get that I suppose.
Or get all the parts from a MOT failure in the UK. I am itching to go there. There can't be any kind of restrictions on shipping them out, and one could claim VAT back at exit.
However, I wonder if I personally had a larger pack, I could use it to my advantage. Ours does the same every day, and always returns with close to 50km on the meter.
The larger pack 'could be' the old Range anxiety creeping in again?.
The big question is Just how big should the pack be?.
There will never be a pack big enough for every owner. Maybe the charging infrastructure has to be as prolific as the old petrol stations have finished up being.
Now there's a thought...
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Post by jake on Oct 5, 2016 19:06:57 GMT 11
I think once the packs get big enough so that you can drive 6 hours in one sitting then that will be big enough for most people. I don't think many people would want to drive longer than that even changing drivers. For me, 3 hours is the maximum.
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Post by stewartm on Oct 6, 2016 9:10:42 GMT 11
I agree Jake, 3 hours is a good point. I have a Cessna 172 with 5+ hours endurance, sadly I make 2 hours before I need a break  |
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